The creation of an Enhanced Geothermal Systems (EGS) reservoir involves fracturing a subterranean formation or a plurality of subterranean formations. Water is circulated from an injection well, through the fractures where it is heated. The hot water or heat from the formation is produced from one or more production wells some distance away from the injection well and used for generating electricity. Fractures within subterranean formations are typically created in an un-cased or open-hole environment by pumping water from the surface down into the well. Water pressure opens a network of fractures in the open-hole section of the subterranean formation having the lowest fracture initiation pressure. The fracture network propagates away from the wellbore in a specific orientation that is related to existing stresses in the subterranean formation. However, a relatively small section of the open-hole section of the subterranean formation is actually fractured. Other locations in the open-hole section having higher fracture initiation pressures that are typically deeper in the subterranean formation remain unstimulated.
Unstimulated regions within the subterranean formation are an untapped source of energy for power generation and the efficiency of power generation on a per well basis remains relatively low. The cost of drilling and completing wells can range from half to 80 percent of the total cost of an EGS project. Therefore, reducing the number of wells for a given project can have a significant impact on the overall cost of the project and ultimately the cost of power production. Understanding the nature of fractures in underground formations also has a significant impact on EGS development.